CHAP. XVIII.] THE NERVOUS SYSTEM. 



211 



ter of the cord is arranged around and between the gray matter, 

 the proportion of gray and white matter varying in different 

 regions of the cord. The white matter, as in the brain, is com- 

 posed of medullated nerves, and the gray matter of nerve-cells 



FIG. 121. TRANSVERSE SECTIONS OF THE SPINAL CORD AT DIFFERENT LEVELS. 

 (Gowers.) (Twice the natural size.) The letters and numbers indicate the position of 

 each section : Ca, at level of coccygeal nerve ; Sac 4 , of 4th sacral ; I s , at third lum- 

 bar, and so on. The gray substance is shaded dark, and the nerve-cells within it are 

 indicated by dots. 



and fine gray fibres, all held together and supported by delicate 

 connective tissue. The majority of the nerves run in a longi- 

 tudinal direction. 



There is no real division between the brain and spinal cord, 



